Should sex education be compulsory ?

In my school when I was 10 years old, we had sex education (including a basic explanation of contraceptive methods) . Actually it was not foreseen but our teacher asked permission to our parents, which did not object. It was actually very nice, because we really had an open discussion.

At 13/14 years old in the Biology program some hours where specially dedicated to sex education ( and a special chapter on “contraceptive methods”).

So when I hear of girls, in West Europe or USA, that remain pregnant very young, and that come from families with a decent education level, I am a little surprised.

Should sex education be taught in primary schools? When should children first start to learn about sex and relationships? Does the responsibility for teaching children about sex lie with their parents?